Polymers can be colored with dyes in various ways. One way is mass coloration of polymers whereby for example a pigment or a dye is mixed with the polymer and the polymer is melted to transport the dye into the polymer matrix. Other processes involve the polymer being colored or, to be more precise, dyed by the dyes defusing into the polymer from a solution or dispersion, examples being the dyeing of polymeric fibers composed of polyether, polyacrylonitrile, polyurethane, cellulose or polyamide for example with, for example, disperse dyes, cationic dyes, acid dyes, metallized dyes or reactive dyes. The use of reactive dyes results in a covalent bond being formed between the dye and the substrate, conferring particularly high fastnesses of the dyeings/colorations. Another way to color a polymer is to add the dye to the polymer's monomers or oligomers, before the polymer is formed or as it is being formed. Dyes capable of forming covalent bonds with the polymer scaffold may result likewise in colorations of high fastness being obtained. For this, the dyes used or, to be more precise, their chromophores have to be sufficiently stable under the conditions of the polymerization. Examples are reactive dyes for polyurethane which are known and are described in DE2259435 and DE2357933 for example. The solubility or dispersibility of the dye used can be significantly influenced through the choice of suitable substituents and be improved by means of suitable side chains such that the use of solvent or dispersant matrix can be greatly reduced or even omitted entirely. Examples thereof are to be found in the documents WO05/000913 and US2004254335.
Commercially available dyes for polymers are usually disperse dyes or solvent dyes and produce, when used for the coloration of polyolefins, colored polyolefins in which the dye often has only low bleed fastnesses. In addition, many of the known dyes have poor lightfastnesses or low thermal stabilities in polyolefins. Dyes having not only good bleed fastnesses but also good lightfastnesses and high thermal stabilities in polyolefins without adversely affecting the properties of the polyolefins used are not known. The dyes known from WO99/24659 do meet the requirements in part, yet it is impossible to achieve dyeings/colorations of high lightfastness with the dyes mentioned.
There is therefore a need for dyes which have the recited properties and thus are useful for the coloration of polyolefins.